diff --git a/cmd/tools/vast/vast.v b/cmd/tools/vast/vast.v
index 1230322173..f6dd918a4f 100644
--- a/cmd/tools/vast/vast.v
+++ b/cmd/tools/vast/vast.v
@@ -1589,6 +1589,7 @@ fn (t Tree) map_init(node ast.MapInit) &Node {
 	obj.add_terse('value_type', t.type_node(node.value_type))
 	obj.add_terse('keys', t.array_node_expr(node.keys))
 	obj.add_terse('vals', t.array_node_expr(node.vals))
+	obj.add_terse('val_types', t.array_node_type(node.val_types))
 	obj.add('comments', t.two_dimension_comment(node.comments))
 	obj.add('pre_cmnts', t.array_node_comment(node.pre_cmnts))
 	obj.add('pos', t.pos(node.pos))
diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index b169da1cf4..aed4c8ccbb 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -1200,6 +1200,7 @@ pub:
 pub mut:
 	keys       []Expr
 	vals       []Expr
+	val_types  []Type
 	typ        Type
 	key_type   Type
 	value_type Type
diff --git a/vlib/v/checker/containers.v b/vlib/v/checker/containers.v
index 39fbb188e9..ff24d3bb86 100644
--- a/vlib/v/checker/containers.v
+++ b/vlib/v/checker/containers.v
@@ -247,6 +247,7 @@ pub fn (mut c Checker) map_init(mut node ast.MapInit) ast.Type {
 			if node.vals[0].is_auto_deref_var() {
 				val0_type = val0_type.deref()
 			}
+			node.val_types << val0_type
 		}
 		mut same_key_type := true
 		for i, key in node.keys {
@@ -258,6 +259,7 @@ pub fn (mut c Checker) map_init(mut node ast.MapInit) ast.Type {
 			key_type := c.expr(key)
 			c.expected_type = val0_type
 			val_type := c.expr(val)
+			node.val_types << val_type
 			if !c.check_types(key_type, key0_type) || (i == 0 && key_type.is_number()
 				&& key0_type.is_number() && key0_type != ast.mktyp(key_type)) {
 				msg := c.expected_msg(key_type, key0_type)
diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 23f9fcaaff..184d07219a 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -4167,9 +4167,9 @@ fn (mut g Gen) map_init(node ast.MapInit) {
 	unwrap_val_typ := g.unwrap_generic(node.value_type)
 	key_typ_str := g.typ(unwrap_key_typ)
 	value_typ_str := g.typ(unwrap_val_typ)
-	value_typ := g.table.sym(unwrap_val_typ)
-	key_typ := g.table.final_sym(unwrap_key_typ)
-	hash_fn, key_eq_fn, clone_fn, free_fn := g.map_fn_ptrs(key_typ)
+	value_sym := g.table.sym(unwrap_val_typ)
+	key_sym := g.table.final_sym(unwrap_key_typ)
+	hash_fn, key_eq_fn, clone_fn, free_fn := g.map_fn_ptrs(key_sym)
 	size := node.vals.len
 	mut shared_styp := '' // only needed for shared &[]{...}
 	mut styp := ''
@@ -4198,7 +4198,7 @@ fn (mut g Gen) map_init(node ast.MapInit) {
 		}
 	}
 	if size > 0 {
-		if value_typ.kind == .function {
+		if value_sym.kind == .function {
 			g.write('new_map_init${noscan}($hash_fn, $key_eq_fn, $clone_fn, $free_fn, $size, sizeof($key_typ_str), sizeof(voidptr), _MOV(($key_typ_str[$size]){')
 		} else {
 			g.write('new_map_init${noscan}($hash_fn, $key_eq_fn, $clone_fn, $free_fn, $size, sizeof($key_typ_str), sizeof($value_typ_str), _MOV(($key_typ_str[$size]){')
@@ -4207,16 +4207,20 @@ fn (mut g Gen) map_init(node ast.MapInit) {
 			g.expr(expr)
 			g.write(', ')
 		}
-		if value_typ.kind == .function {
+		if value_sym.kind == .function {
 			g.write('}), _MOV((voidptr[$size]){')
 		} else {
 			g.write('}), _MOV(($value_typ_str[$size]){')
 		}
-		for expr in node.vals {
+		for i, expr in node.vals {
 			if expr.is_auto_deref_var() {
 				g.write('*')
 			}
-			g.expr(expr)
+			if value_sym.kind == .sum_type {
+				g.expr_with_cast(expr, node.val_types[i], unwrap_val_typ)
+			} else {
+				g.expr(expr)
+			}
 			g.write(', ')
 		}
 		g.write('}))')
diff --git a/vlib/v/tests/map_sumtype_value_init_test.v b/vlib/v/tests/map_sumtype_value_init_test.v
new file mode 100644
index 0000000000..f185446e3c
--- /dev/null
+++ b/vlib/v/tests/map_sumtype_value_init_test.v
@@ -0,0 +1,18 @@
+type Child = Tree | string
+
+struct Tree {
+	name  string
+	child map[string]Child
+}
+
+fn test_map_sumtype_value_init() {
+	tree := Tree{
+		name: 'foo'
+		child: {
+			'a': 'value'
+		}
+	}
+	println(tree)
+	ret := tree.child['a'] or { Child('') }
+	assert ret == Child('value')
+}